The present invention relates to a novel cast polyolefin film or oriented polyolefin film having an embossed surface. More particularly, the present invention relates to an embossed cast polyolefin film or an embossed biaxially oriented polyolefin film, wherein the cast film or the oriented film may optionally be metallized to produce final films that are suitable for various applications including prismatic or holographic packaging materials.
Films having a prismatic or holographic appearance are already known in the art. These conventional films, however, are dominated by polyester films, which are able to handle the high temperatures needed for this application and provide a visually appealing and strong finished product. The advantage to using the film of the present invention (e.g., a biaxially oriented polypropylene film), however, is primarily in the economics. The polyolefin films (e.g., OPP) of the present invention are less dense than those films made from polyethylene terephthalate, and thus they offer cost savings to the purchaser in an improved yield for the same amount of film by weight. They are also more easily tailored for advantages or benefits in terms of physical properties such as sealability, oxygen and water barrier properties, coefficient of friction, or printability.
The film of the present invention has been tailored to provide a substrate that is easy to emboss, provides a brilliant embossed and metallized surface and also contains a high energy treated surface on the unembossed side for further converting.
U.S. Pat. No. 5,194,318 to Migliorini, et al. discloses a metallized oriented thermoplastic film combination comprising a propylene homopolymer or copolymer substrate (B) having a high density polyethylene (HDPE) skin layer (A) on at least one side thereof, wherein the polyethylene has a thin metal layer deposited thereon. In a preferred embodiment, the use of a heat sealable polymer layer (C) on one side of substrate (B) is also disclosed.
U.S. Pat. No. 4,961,992 to Balloni, et al. discloses a laminated film including first and second webs, the first web including a core layer and a surface layer, the surface layer of the first web containing an effective amount of polydialkylsiloxane to reduce the coefficient of friction thereof, and an adhesive layer bonding the first and second webs to each other. The patent further discloses that the surface or skin layers of each web are sealable, and preferably heat sealable, and that the polydialkylsiloxane is transferred from the skin layer of the first web to the skin layer of the second web in order to reduce the coefficient of friction thereof.
U.S. Pat. No. 4,413,109 to Haas discloses an embossed ethylene-propylene copolymer film having a thickness of less than or equal to 24 microns. The film is made by blow-extruding the ethylene-propylene copolymer into a tubular web, pinching the tubular web between pinch rolls, and embossing the pinched web by passing it between an embossing roll and a pressure roll.
The above-described patents, however, do not disclose an embossed cast film or biaxially oriented film as claimed in the present invention.
It is an object of the present invention to provide an embossed, oriented polyolefin film that may be metallized to produce a final film having a prismatic or holographic appearance.
It is an alternative object of the present invention to provide an embossed, cast polyolefin film that may be metallized to produce a final film having a prismatic or holographic appearance.
It is another object of the present invention to provide an embossed cast polyolefin film or an embossed, metallized, biaxially oriented polyolefin film having a shiny, metallic prismatic or holographic appearance.
It is a further object of the present invention to provide an embossed cast polyolefin film or an embossed oriented polyolefin film having a high energy surface on the unembossed side, wherein the high energy surface may be further converted after metallization.
It is yet another object of the present invention to provide a process for producing an embossed cast polyolefin film or an oriented polyolefin film that has a brilliant embossed appearance without leaving any residue on the embossing machine.
In accordance with these and other objects of the present invention, an embossed cast polyolefin film or an embossed oriented polyolefin film is provided, wherein the film comprises:
(a) a core layer comprising a propylene polymer;
(b) an embossed outer layer on one side of said core layer, said embossed outer layer comprising an olefin polymer capable of being embossed; and
(c) an additional outer layer on a side of said core layer opposite to said embossed outer layer, said additional outer layer comprising an olefin polymer.
In a preferred embodiment of the present invention, the embossed surface of the film of the present invention is metallized to provide a final film having a shiny, metallic prismatic or holographic appearance.
In another preferred embodiment of the present invention, the embossed outer layer (b) and/or the additional outer layer (c) may constitute the skin layers of the film.
In yet another preferred embodiment of the present invention, a cast polyolefin film or an embossed biaxially oriented polypropylene film is disclosed, wherein the film comprises:
(a) a core layer comprising a propylene homopolymer or copolymer;
(b) an embossed outer layer on one side of the core layer, said embossed outer layer comprising an ethylene-propylene-butylene (EPB) terpolymer or an ethylene-propylene (EP) copolymer; and
(c) an additional outer layer on a side of said core opposite to said embossed outer layer, said additional outer layer comprising a high density polyethylene (HDPE), the surface of which is optionally treated to aid in further converting.